The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Most modern aircraft have stability augmentation systems to enable fly-by-wire operation. Furthermore most, if not all, state-of-the-art high-performance military aircraft have advanced specialized control augmentation systems with selectable task-tailored control laws. Such systems enable the pilot to maneuver the aircraft to its performance limits and perform tasks such as precision tracking of targets.
It is extremely important that the aircraft and its subsystems, including the augmented control system, are accurately modeled to support design and performance assessment efforts. However, at the same time, most high-performance and precision flight applications are capable of generating control surface actuator performance requirements that exceed the capability of state-of-the-art actuator technology, which primarily involves electro-hydraulic actuators.
Performance limitations of present day electro-hydraulic and electromechanical actuators are predominantly bandwidth related. These performance limitations are typically due to size, weight, power and cost relating to such actuators. Such actuators also suffer from inherent characteristics such as high levels of backlash, hysteresis and nonlinearity due to variables such as gear heads, actuator linkages, hydraulic fluid viscosity, aging etc. Additionally, the ability to determine the health of the closed-loop actuators of the aircraft is highly important to achieving mission objectives and ensuring safe operation of the aircraft.
With present day systems, one specific drawback is the inability to identify a primary control surface malfunction before it can destabilize an aircraft. Another drawback is the inability to verify and validate aircraft control systems during flight. Design, verification and validation of aircraft require understanding the dynamic behavior of the aircraft and control system. This is traditionally achieved through ground vibration tests, wind tunnel tests, simulated hardware in the loop tests, and flight testing. These tests can be extremely expensive, require specialized equipment, and have limitations with respect to the feasibility of using excitation test signals that have sufficient bandwidth and that can be decoupled from the systems being measured. Existing solutions rely on the aircraft control system to generate test signals. Thus, there presently is no way to independently assess the aircraft's control system during these tests.